The present invention relates generally to self-propelled booms which carry at the tip end of the boom either a work platform or a work attachment. More particularly, the present invention relates to a self-propelled boom vehicle with extendible axles and with associated extendible steering linkage.
It is known in the prior art to provide a self-propelled boom vehicle with extendible axles. The purpose of extendible axles is to widen the stance of the vehicle to increase its resistance to overturn and to increase its working load characteristics.
One prior art technique for extending the axles for a self-propelled boom is to use the main boom to react against the ground, thus lifting one end of the chassis. With that end of the chassis elevated above the ground, that axle is extended. The boom is then used to lower the chassis and then the boom is swung 180.degree. before repeating the process at the opposite end of the chassis. Disadvantages of this technique include excessive wear of the boom slide pads and the need for a large clear area to swing the boom from one end to the other. That technique also has the potential for extensive damage from operators using the same process to extend the axles to attempt to push the machine out from a position in which it is stuck. The additional disadvantage is the time that the process requires to complete extension of the axles.
It is also known in the prior art to provide relatively large and heavy chassis mounted hydraulic jacks for self-propelled booms to lift sequentially each end of the chassis, extend the axle, then lower that end of the chassis before repeating the process for the opposite end. Disadvantages of this technique include the cost of the two large jacks and the requirement in soft ground conditions to provide the necessary shoring underneath the jack feet. This technique also requires considerable time to accomplish the extension of both axles. In each of these prior art techniques, the operator is required to exit the platform and to leave the controls of the vehicle to perform certain functions from the ground in order to extend the axles. This inherently involves further waste of time in extending the axles.
In contrast to these two described techniques for extending self-propelled boom axles, the present invention quickly and efficiently extends the axles while the axles are supporting the full weight of the vehicle. Furthermore, the present invention does not require the operator to either leave the controls of the vehicle or, if the vehicle contains a work platform, the operator need not exit the work platform in order to extend the axles. The present invention also includes the inherent advantage in requiring no independent action from the operator which must be conducted from the ground. Those operations, such as the insertion or removal of pins, may cause injury or damage to the vehicle or property if the operator neglects to perform the required functions.
The prior art also includes agricultural spraying equipment with extendible axles. The Balmer U.S. Pat. No. 5,039,129 dated Aug. 13, 1991 teaches a field sprayer having two forward and two rear extendible axles. The axles are extendible horizontally on the go. However, the design of that prior art patent requires a two part chassis wherein the forward, steerable section of the chassis must be pivotally connected to the remainder of the chassis. The steering mechanism of that patent is accomplished by the use of a diagonally mounted steering cylinder which causes the two pivotally connected chassis sections to articulate relative to each other. That steering mechanism would be woe-fully inadequate for a self-propelled boom. Firstly, the use of two pivoting chassis sections would reduce the vehicle's resistance to overturn. Secondly, the articulating chassis would be prohibitively expensive for the relatively large vehicle weights and working loads achieved by the present invention. Thirdly, a steering mechanism requiring the rotation of the entire forward axle around a vertical axis would inherently cause unexpected lateral motion of an extended boom simply by turning the steering control to the left or right. Such a steering mechanism is simply unworkable for a self-propelled boom vehicle.
Another prior art row crop applicator is shown in the Torborg U.S. Pat. No. 5,489,113. That patent teaches an extendible axle but the mechanism requires the use of two separate cylinders for each axle, both of which are mounted on the exterior surface of the central, fixed axle section. The outer end of the cylinders connects through a linkage mechanism to the movable, extendible axle members. The use of exterior mounted cylinders is definitely a disadvantage in self-propelled booms such as in the present invention. Exterior mounted cylinders would be exposed to damage, and to the natural elements as well as to dust and debris commonly experienced at construction work sites. The Torborg linkage connection between the cylinder and the movable axle section is relatively cumbersome. The present invention provides a single interior mounted cylinder, both ends of which are attached to movable axle sections and the cylinder acts directly on both movable axle sections without any intervening linkage. The system of the present invention protects the hydraulic cylinder from the elements as well as from job site dust and debris. By using only one cylinder, the present invention minimizes the working components, resulting in a much more dependable extension mechanism. Furthermore, the present invention avoids bending loads being applied to the cylinder. Since the extendible axle arms of the present invention are exposed to large bending loads and deflection, it is important to position the cylinder to avoid those bending loads. The present invention in effect provides a "floating" cylinder mount by connecting both cylinder ends directly to the extendible axle arms. This direct and floating mounting of the cylinder also allows the axle arms to extend sequentially, i.e., the axle will extend in the direction of least resistance. The sequential extension allows all of the cylinder's power to be utilized to extend the second axle arm after the first arm is fully extended.
The Torborg '113 patent also teaches a hydraulically adjustable tie rod which modifies the steering linkage as the axle is extended. However, the Torborg mechanism requires that the operator leave the controls of the vehicle to fine tune the steering toe-in by manually rotating hex nuts 36. The present invention provides an adjustable steering linkage in the form of a master and slave cylinder arrangement and wherein an automatic resynchronizing system is included to automatically resynchronize the steering.
The Torborg U.S. Pat. No. 5,454,583 teaches an agricultural vehicle wherein the axles are adjustable and wherein an autotracking system is provided which automatically insures that the rear axle is set to the same width as the forward axle.
A primary object of the present invention is to provide a self-propelled boom with extendible axles wherein the axles are extendible while simultaneously carrying the weight of the vehicle and without requiring the operator to exit the work platform or to leave the controls of the vehicle in order to extend the axles.
Another object of the invention is to provide a self-propelled boom with extendible axles wherein the extension mechanism for each axle includes a single hydraulic cylinder which is carried internally of the axle and which is mounted at both of its ends to the outwardly extendible arm sections.
Another object of the invention is to provide a self-propelled boom with extendible axles and with an automatically self-adjusting steering control mechanism.
A still further object of the invention is to provide a self-propelled boom with extendible axles and self-adjusting steering wherein the steering automatically resynchronizes itself as the steering is moved to either left or right lock position.
Other objects and advantages of the invention will become apparent from the following description and drawings wherein: